In a statement Wednesday, State Department spokeswoman Heather Nauert said the US had made this decision on Monday, and accused Russia of violating international law. The statement anticipated the sanctions would go into effect around Aug. 22 in line with the Chemical and Biological Weapons Control and Warfare Elimination Act of 1991.
The State Department notified Congress on Wednesday of the first of two potential tranches of sanctions required under the 1991 law. Unless Russia takes certain steps, a second set of penalties -- more stringent than this first round -- must follow, according to the law.
The first set of sanctions targets certain items the US exports to Russia that could have military uses -- so-called dual use technologies. These are sensitive goods that normally would go through a case-by-case review before they are exported. With these sanctions, the exports will be presumptively denied.
A senior State Department official said there would be carve-outs however.
The US would then require Russia to assure over the next 90 days that it is no longer using chemical or biological weapons and will not do so in the future. Additionally, the criteria in the law call for Russia to allow on-site inspectors to ensure compliance.
The official said that if Russia did not meet the demands, the US "will have to consider whether to impose a second tranche of sanctions as specified by the statute."
Dmitry Polyanskiy, first deputy permanent representative of Russia to the UN, dismissed the sanctions in a tweet on Wednesday responding to the news.
"The theater of absurd continues. No proofs, no clues, no logic, no presumption of innocense, just highly-liklies. Only one rule: blame everything on Russia, no matter how absurd and fake it is. Let us welcome the United Sanctions of America!" Polyanskiy tweeted.
The United Kingdom welcomed the move from the US on Wednesday. In a short statement, a government spokesperson said, "The strong international response to the use of a chemical weapon on the streets of Salisbury sends an unequivocal message to Russia that its provocative, reckless behaviour will not go unchallenged."
A former Defense Department official, Mark Simakovsky, said a second tranche would target Russian exports to the US and theoretically could include flights by the state airline Aeroflot as well as a downgrade of diplomatic relations. Simakovsky said he was highly skeptical a second round would be applied. That said, he added, "I don't think this is the last shoe to drop" because of political pressure, criticism from Democrats and the looming midterm elections.
"I'm highly skeptical the administration will cut off a whole range of imports and exports, but that's the interesting thing," Simakovsky said. "What will the administration do in three months?"
Sanctions under this 1991 law have been applied in the past against Syria for its 2013 use of chemical weapons and against North Korea for its use of VX nerve agent in a Malaysian airport during the assassination of Kim Jong Un's half brother.
A senior State Department official said the first tranche of the sanctions could impact "potentially a very great sweep of the Russian economy." The official said firms affected account for 70 percent of the Russian economy and 40 percent of its workforce.
"It is possible the trade affected could reach hundreds of millions of dollars," the senior official said. He added that "it also depends on what Russian entities apply to export."
Simakovsky said he was "skeptical of the high amount" of that estimate.
Simakovsky said the sanctions were likely driven by the political climate, particularly pressures stemming from President Donald Trump's performance in July at his summit in Helsinki, Finland, with Russian President Vladimir Putin.
"This clearly reinforces that the administration is tightening its sanctions approach to Russia," he said. He noted that "they could have taken this step months ago. They were late in taking this step by several months. The fact that they're doing it now showcases that they're under increased political pressure to target Russia for its malign activities abroad."
CNN's Radina Gigova and Sebastian Shukla contributed to this report.